Hydrocyclones are used to separate solid particles from liquids in suspensions based on density and coarseness (i.e., size). Hydrocyclones may also be used to separate two liquid phases having different densities. Typical hydrocyclones include a cylindrical section disposed above a conical base. The suspension or mixture is fed tangentially into the cylindrical section. The hydrocyclone has a small opening at the bottom apex of the conical base through which the underflow exits the hydrocyclone. The hydrocyclone also has a larger opening at the top of the cylindrical section through which the overflow exits. The underflow is generally the denser or coarser portion of the suspension or mixture, while the overflow is generally the lighter or finer portion.
Hydrocyclone units, such as desanders and desilters, are used to remove drill cuttings from drilling fluid. Because air is sucked through the opening at the apex of the conical section during use, air is introduced into the drilling fluid in the hydrocyclones. This entrained air adversely affects the quality of the drilling mud.